Patients having such conditions as heart failure or decreased kidney function requiring dialysis often have undesirable fluid accumulation in the body. In general, fluid accumulation is a failure or over-response of the homeostatic process within the body. The body normally prevents the build up of fluids by maintaining adequate pressures and concentrations of salt and proteins and by actively removing excess fluid. Fluid accumulation can occur, for example, when the body's mechanisms for preventing fluid accumulation are affected by disease, such as heart failure, left sided myocardial infarction, high blood pressure, altitude sickness, emphysema (all which affect pressures), cancers that affect the lymphatic system, kidney failure, and diseases that disrupt the protein concentrations. As a result, providing an adequate monitor of the patient's fluid status can provide physicians and patients with a better tool to manage disease.
Patients with conditions that contribute to fluid accumulation in the body often regulate the level of accumulated fluid through the use of diuretics. This can be a delicate balancing act, since fluid accumulation can result in frequent and lengthy hospitalization and overuse of diuretics or other fluid reduction tools can result in dehydration. In some case, dehydration may become so severe as to result in hypovolaemic shock, including: diminished consciousness, lack of urine output, cool moist extremities, a rapid and feeble pulse (the radial pulse may be undetectable), low or undetectable blood pressure, and peripheral cyanosis.